234 BULLETIN 201, UNITED STATES NATIONAL MUSEUM 



The habits of A. anophelinae are extremely interesting and special- 

 ized. It was discovered in the holes made by the large shore crab, 

 Cardisoma crassum Smith, living with the larvae of a mosquito Deino- 

 cerites pseudes Dyar and Knab (1909, p. 260). According to Knab, 

 the collector (1906, p. 95), these mosquitoes were found far up 

 the mangrove inlets behind Puntarenas. The crab holes were near 

 the head of tide water, above overflow, often a considerable distance 

 from the water, and the water in them must have been very nearly if 

 not quite fresh. The mysid Antromysis anophelinae must, therefore, 

 be regarded as a brackish-water form at least, with a wide range 

 of salinity tolerance up to water that is occasionally quite fresh. The 

 reduced and specialized structure of the eyes is a point of great in- 

 terest. Knab does not mention the depth of the crab holes at Punt- 

 arenas, but he says that similar holes at Port Limon on the east 

 coast of Costa Eica, inhabited by Deinocerites cancer, went to a great 

 depth to reach water, so that the mosquitoes living in them never see 

 the light until they attain the winged state. There were no mysids 

 in the holes at Port Limon, but if the holes at Puntarenas were sim- 

 ilarly deep and dark, the reduction of the eye can be correlated with 

 this specialized habit. The type species, A. cenotensis, is a cave- 

 dwelling species, found in fresh water in caves in Yucatan, and in this 

 species the eyes are further reduced and have lost all pigment. A. 

 cenotensis has probably been derived from a species similar to A. 

 anophelinae in which the first stages of specialized habit with the 

 corresponding specialization of structure are exhibited. 



ANTROMYSIS CENOTENSIS Creaser 

 Antromysis cenotensis Creaseb, 1936, p. 121, figs. 13-24 ; 1938, p. 159. 



Occurrence. — Paratypes * from Yucatan, identified by E. P. 

 Creaser. 

 Distribution. — Known only from caves in Yucatan. 



Tribe HETEROMYSINI 



Endopods of the third to the eighth thoracic limbs with the carpus 

 and propodus fused; the fused carpopropodus is undivided in the 

 third pair of limbs but is divided by vertical articulations into a num- 

 ber of subjoints in the fourth to the eighth pair; all the pleopods of 

 the male rudimentary as in the female; antennal scale ovate, setose 

 all around ; telson cleft. 



Remarks. — Only one genus is included in this tribe Heteromysis. 

 Numerous species of the genus have been described, of which three, 

 possibly four, are known from American waters. 



